Most implantable stimulation devices, such as pacemakers and ICDs, use one or more implantable stimulation leads that electrically connect the stimulation device to a desired body tissue location. There are numerous types of implantable stimulation leads, just as there are numerous types of implantable stimulation devices. Implantable stimulation leads include sensing/pacing leads, shocking leads, epicardial leads, endocardial leads, atrial leads, ventricular leads, unipolar leads, bipolar leads, and the like.
All implantable stimulation leads include one or more electrodes at a distal end of the lead, and an electrical connector at a proximal end of the lead. The distal electrode is adapted to physically and/or electrically contact body tissue at a desired monitoring and/or stimulating location. Active or passive fixation means may also be included as part of the lead at or near the distal end in order to secure the electrode in its desired tissue-contacting location. The proximal connector is adapted to interface with the implantable stimulation device. Connecting the distal electrode to the proximal connector is the lead body. The lead body comprises one or more flexible electrical conductors, surrounded or otherwise protected by an appropriate insulating sheath, which establishes electrical connection between the distal electrode and the proximal connector. As used herein, and as is conventional when describing implantable stimulation leads, the “distal” end of a lead is the end farthest from the stimulation device, and the “proximal” end is the end closest to, and usually the end connected to, the stimulation device.
When an implantable stimulation lead is first implanted in a patient, there are some preliminary electrical tests that should be performed before the lead is finally attached to its corresponding stimulation device. For example, if the lead is a pacing lead that is to be connected to an implantable pacemaker, then the lead is first implanted (e.g., transvenously) so that the distal electrode is in electrical contact with cardiac muscle tissue. Then, before the proximal connector of the lead is secured to the pacemaker, the proximal connector is temporarily connected to an appropriate testing device (e.g., a patient system analyzer) so that a series of stimulation pulses of varying energies, or other test signals (such as signals to measure the lead impedance), can be applied to the cardiac tissue through the lead in order to ascertain the capture threshold at which the cardiac muscle tissue contracts, or in order to determine other parameters associated with the lead. The results of such capture threshold testing, or other testing, advantageously provide an indication as to whether the distal electrode is making good contact with the body tissue, as well as what the initial setting of the stimulation energy of the pacemaker should be.
If the lead is a shocking lead, also referred to as a defibrillation lead, then typically at least two shocking leads are implanted so that the distal electrodes contact the appropriate cardiac tissue. The distal electrodes may comprise patch electrodes or any other appropriate shocking electrodes. The proximal connectors of such leads are then temporarily connected to an appropriate testing device, typically referred to as a “defibrillation system analyzer (DSA)”.
The defibrillation system analyzer applies an appropriate signal (usually a low amplitude AC signal) to the shocking electrodes in order to induce fibrillation. Shocking pulses of varying energies are then applied to the cardiac tissue across the shocking electrodes in order to ascertain the defibrillation threshold, i.e., the amount of energy required in a defibrillation shock pulse in order to defibrillate the heart. Such defibrillation threshold is then used to guide the initial setting of the defibrillation energy generated by the ICD.
Although the present invention is directed primarily towards a universal cable connector for temporarily connecting implantable shocking leads and implantable shocking devices with a defibrillation system analyzer, it may be appreciated that the present invention may also be used with implantable pacing leads, an implantable pacemaker and a patient system analyzer (i.e., a system analyzer which is used to test an implantable pacemaker or ICD). Thus, it shall be understood that “implantable stimulation leads” shall include both pacing and shocking leads, “implantable stimulation device” shall include both pacing and shocking devices, and “system analyzers” shall include both pacing and defibrillation system analyzers.
Proximal connectors used with most implantable stimulation leads are typically one of two types: unipolar or bipolar. Unipolar proximal connectors include a single proximal tip electrode (male connector) adapted to be inserted into an appropriate conductive annular ring or other receiving receptacle (female connector) located on or in the implantable stimulation device. Secure physical and electrical contact between the male and female connectors is typically obtained using a setscrew. That is, the setscrew is threadedly mounted in the female connector and is tightened against the male connector so as to firmly hold it in physical and electrical contact with the female connector. In order for a proper connection to be made, it is necessary that the male connector and female connectors be of the same size.
Bipolar proximal connectors typically include a proximal tip electrode the same as is used in proximal unipolar connectors, and also include a proximal ring electrode, that is an annular conductive ring that is spaced-apart from the tip electrode. The receiving, or female bipolar, connector thus comprises an appropriate receiving channel having separate conductive elements therein that establish a secure physical and electrical connection with the proximal tip and ring electrodes of the lead. A setscrew, or equivalent, may also be used to secure one or both of the tip and ring electrodes within the female connector.
Some effort has been made in recent years to standardize the size of proximal connectors used with pacing leads. However, there still exists a wide variety of different sizes and types of proximal connectors that are used with implantable stimulation devices. Further, the size of proximal connectors used with shocking leads is typically different than the size of proximal connectors used with sensing/pacing leads. Hence, in order to connect the different sized proximal connectors to a system analyzer (or equivalent testing device) during the implant procedure, it has heretofore been necessary to use a plurality of cables, connector blocks, and/or a plurality of lead adapters for each size or type of proximal connector that may be encountered.
Connection of implanted stimulation leads to a system analyzer in the prior art typically consists of two sets of cables and connector blocks; one for shocking and one for pacing functions. Each connector block of the prior art typically includes two female connectors to which two corresponding proximal male connectors of the implanted stimulation leads may be temporarily attached. Such temporary attachment is typically achieved by using setscrew connectors mounted to the connector block that receive and grip the male tips of the implanted leads. A cable, usually hard-wired to the connectors at one end and having a multi-pin connector at the other end, then provides the appropriate electrical interface between the connectors and the system analyzer. Unfortunately, the connectors used on such adapters are still size-dependent (i.e., there is no single female connector to which all sizes of proximal lead male connectors can be safely connected). Hence, different lead adapters must still be used for different sized leads. Thus, a substantial inventory of lead adapters must be maintained for use in the operating room where the implant procedure is being carried out. Further, any such adapters which are used must be sterile, which requires a separate sterilizing operation. Moreover, the use of such adapters increases the risk of damage and/or connection error. That is, the frequent connecting and disconnecting of the proximal connectors to and from the setscrew or other female connectors of the lead adapters, can, if not carefully carried out, damage the proximal connectors, particularly the delicate proximal ring electrode, thereby rendering the implanted lead unsuitable. Further, there is always the chance when leads are frequently disconnected and re-connected that an error will occur in the polarity of the connections that are made.
Hence, there is a need in the art for a way to safely and efficiently connect the various sizes and types of proximal connectors existing on implanted stimulation leads to a system analyzer (or other testing device) used during the implant procedure. In short, there is a need for a universal connector that can be used with all implanted leads.
Further, it is desirable to test the performance of the implantable stimulation device prior to finalizing, its implantation, i.e., prior to sewing up the patient at the conclusion of the implant operation. When the implantable stimulation device is an ICD, it is preferable that the ICD be connected to the implanted leads at the same time that the system analyzer is connected to the ICD in order to monitor its performance, particularly to monitor the output energy delivered by the ICD. Typically, the state-of-the-art requires that such output energy monitoring can only be accomplished by using some sort of in-line lead adapter, e.g., a “Y” adapter that connects the output of the ICD to both the implanted shocking leads and to the system analyzer. The use of such adapter, which must be sterile, requires additional connecting and disconnecting of the implanted lead, which additional connecting and disconnecting may further damage the proximal male connector of the lead or the corresponding female connector of the ICD. Further, such additional connecting also increases the possibility that a connection of the incorrect polarity will be made. A connection of the improper polarity could, where large shocking energies are used by an ICD, easily damage the system analyzer and/or the ICD, and could be harmful to the patient.
What is clearly needed, therefore, is a way to easily and safely test the performance of the ICD, including testing the output energy delivered by the ICD, after the shocking leads have been implanted and connected to the ICD. Accompanying this need is the need to perform such testing without the use of any special adapters that require additional disconnecting of the leads from the ICD and without the possibility of making a mistake in the polarity of the connection.
Thus, in summary, to minimize the risk of lead damage or polarity connection error, what is needed is an implant procedure or technique wherein the implanted leads may be detachably connected to the system analyzer without using adapters or other holding mechanisms that could damage the leads; and wherein once the leads have been tested by the system analyzer, the leads may be connected to the ICD (or other stimulation device) just once, yet that still allows the ICD to be fully tested after the leads have been so connected, including the testing of the output energy delivered by the ICD, without concern for whether a proper polarity has been achieved between the ICD and the system analyzer.
In one known instance, an ICD clamp assembly is designed to be used with the cable connector block that permits an in-line electrical connection of the proper polarity to be established between the ICD and the cable connector block after the implanted leads have been connected to the ICD. Advantageously, the ICD clamp assembly includes a clamp that simply clamps over the ICD and establishes electrical contact with the setscrews or other securing means used to secure the proximal terminal of the shocking leads to the ICD, thereby providing the desired in-line electrical connection without the use of any adapters that require the disconnecting of the shocking leads from the ICD. Moreover, the clamp is specially configured so that it can only clamp over the ICD and make contact with the shocking lead setscrews in one orientation, thereby assuring that the resulting electrical connection is of the proper polarity. The clamp connector of the clamp assembly is electrically connected to the connector block through a cable and keyed plug, thereby further assuring that the proper polarity is maintained at the cable connector block. Hence, by simply clamping the clamp over the ICD, plugging the keyed plug of the clamp assembly into the cable connector block, and connecting the cable connector block to the system analyzer, the system analyzer can monitor the performance of the ICD including the output energy delivered by the ICD without concern for whether a proper polarity connection has been established between the ICD and the system analyzer.
However, with the introduction of a relatively recent standard known as IS-4 (officially “active implantable medical devices—four-pole connector system for implantable cardiac rhythm management devices”) calls for seals to be placed in the connector cavity and not on the lead connector, known techniques of connection have had to be reconsidered. Specifically, with the development of the new IS-4 or similar lead wires, alligator clips and the like can no longer be used because the ring contacts are too close to each other and may cause electrical shorting.
It was in light of the foregoing that the present invention was conceived and has now been reduced to practice.